I know all about reconstruction filters. I asked the question rhetorically so as to illustrate to others that there was an ambiguity in interpreting what the stored waveform really is.

Nope - believe me, your example if antialiasing filter was used and reconstruction filter was used provide always sine - don't ignore Nyquist as it works perfectly.
Use opencalc (or excel) and verify your signal - use spline or cubic line smoothing to simulate lowpass filter.

Quote:

Originally Posted by mc6809e

If the Amiga had been built with a programmable reconstruction filter that could be tuned to the waveform output frequency, then it would be a sample player.

That fact that it only has a couple of gently sloping fixed low pass filters (and even one of these can be turned off) tells us that simple signal reconstruction and playback was not entirely the goal. Synthesis was also the goal.

Nope - believe me, your example if antialiasing filter was used and reconstruction filter was used provide always sine - don't ignore Nyquist as it works perfectly.
Use opencalc (or excel) and verify your signal - use spline or cubic line smoothing to simulate lowpass filter.

A two point square wave output at 1000 points per second requires a low pass filter with a cutoff frequency of 500 Hz to construct a sine wave. There is no such filter on the Amiga. The cutoff frequency is much higher. To get perfect reconstruction of the original signal, the cutoff frequency must be half the the output frequency and since on the Amiga the output frequency is variable, we'd also have to have a programmable filter.

Oh sure. For the highest output rates, the low pass filter starts to be effective as a reconstruction filter. For lower rates, not much at all.

And maybe that's why this discussion has been so contentious. At higher output rates, the Amiga audio hardware performs more like a sample player. At lower output rates it looks more like a synthesizer. The Amiga gives us the choice.

A two point square wave output at 1000 points per second requires a low pass filter with a cutoff frequency of 500 Hz to construct a sine wave. There is no such filter on the Amiga. The cutoff frequency is much higher. To get perfect reconstruction of the original signal, the cutoff frequency must be half the the output frequency and since on the Amiga the output frequency is variable, we'd also have to have a programmable filter.

This is only partially correct - filter is present but his efficiency may be not enough to completely fulfill reconstruction requirement, also it is very important to understand that aliasing is introduced in ADC not in DAC thus even not efficient enough reconstruction filter will perform correctly if signal is without aliasing.

Quote:

Originally Posted by mc6809e

Oh sure. For the highest output rates, the low pass filter starts to be effective as a reconstruction filter. For lower rates, not much at all.

And maybe that's why this discussion has been so contentious. At higher output rates, the Amiga audio hardware performs more like a sample player. At lower output rates it looks more like a synthesizer. The Amiga gives us the choice.

Thanks for the link!

Once again - aliasing is introduced when signal is sampled with to low sample rate i.e. in ADC - DAC will reproduce signal without aliasing even if reconstruction filter is not efficient enough - DAC without oversampling (Amiga case) will introduce additional loss for high frequency signal http://www.maximintegrated.com/app-n...ex.mvp/id/3853 - this can be compensated in analog reconstruction filter or compensated in digital stage (or by additional digital filter before DAC or by software filter that modify samples itself - then you need additional room (bit or 2) or you are forced to accept lower level of signal (peak and rms)).